The intricacies of watering a city

Posted at 2:00pm Sunday 07 Jan, 2018

Water, water everywhere and not a drop to sprinkle.

It was a fair old dumping. Nearly 22ml of rain in just 12 hours with a deepening low pressure system promising another 150ml the next day.

“But it doesn't really help us,” says Rodney Clark, the man who runs Tauranga City's water supply. “It doesn't fill tanks.”

It seemed the heavens were delivering to a city where garden sprinklers are dirty words, certainly prohibited, where hosing paths and driveways is as anti-social as it is against the bylaws, and you can only “carefully” hose by hand before breakfast and after dinner.

And if that didn't scare us into more conservative water usage then total hose bans might. And possibly a ban on all outdoor water use.

“All of our pristine double A-graded drinking water being dumped on lawns,” says Rodney. He suggests some alternatives for the lawn proud and passionate – like rain water harvesting or installing a bore.

To understand the Tauranga City Council water restrictions brought on by sustained and increased water demand and hot dry weather, it helps to understand the process. And why a day's rain does and doesn't help.

Tauranga has two streams supplying water – the Waiorohi on Oropi Rd and the Tautau at Pyes Pa.

“Good rivers, good water,” says Rodney. “An ample supply of raw water all year, every year. We draw off the water, treat it and put it in storage.”

That storage is replenished every day. And what is produced today is drunk tomorrow, normally about 39 million litres.

And at any given time there's two to three days of off-peak storage ready to go to town, ready to drink. But when summer comes early, like this year, when the big hot dry comes to town early in September, water engineers can get palpitations.

There's a sustained and increasing demand for water. A lot of people are irrigating lawns and gardens, holidaymakers are flocking to town driving up consumption of the precious AA-graded water to 52.5 million litres. That tests man and machine.

“It's not the supply of water, but our capacity to treat it. Then two or three days of treated water storage becomes one or two days.”

So if we know we are going to crack 50 million litres a day, why don't we have the machinery to cope?

“We have a system in place to deal with normal demand of about 39 million litres – but to expect a city to put in place something that can run over 50 million litres like we have experienced, would be quite expensive.”

Up until Wednesday the seven-day rolling average consumption of treated water in Tauranga was nearly 43 million litres. “And when you are running machines at high capacity for long periods, maintenance starts to back up. You have to throttle off to do ongoing maintenance,” says Rodney.

He likens it to endlessly driving a car at 200km/h. “You can't not expect to pull over and change the oil every now and again.”

And when the machines cracked 50 million litres a day early this summer – or “very high” – and there's not much rain in the forecasts, restrictions were imposed.

That spike - this summer's usage cracks the red “very high” line. Last year's usage is in grey.

“It worked, achieved exactly what was intended,” says Rodney. Consumption dropped considerably – down almost 10 million litres a day – and that's very manageable. “Yep, it's been raining this week and that's good for us because it slows consumption.” Rain means people stop frittering high quality drinking water.

“But it doesn't fill any tanks anywhere because we have got two good rivers whether it's raining or not.” Again, the problems more about the capacity to treat the water and the fact there's only one or two days' storage of treated drinking water ready to go.

The engineers don't like to put a number on how much water they can produce, here are many variables. “But if we are pushed up around that 50 million litre mark, then we are tapped out,” says Rodney.

“But we are very proud of our plants which produce high quality AA-graded drinking water.” Even if it is getting dumped on lawns, and driveways and paths.”

But it seems Tauranga has responded with good grace to the restrictions – well, mostly. A few people aren't happy, but most have complied.

“You can takes things like water for granted if you don't understand that it's a finite resource and you are flicking the sprinkler on, leaving it on and forgetting about it. Quite easy to do.”

But the restrictions are serving as a “nice reminder” – hang on, we need to be a bit more conservative with what we are using.

And if the reminders don't register, then there are the self-appointed bylaw enforcers, the double-A water vigilantes, taking a very personal responsibility for out water conservation. “They've been helping us out and letting us know where people aren't complying.”

So another reminder – you are probably being watched.

“The key messages are we have an ample water source, but it's the throughput to treat the water,” says Rodney. “And storage-wise we have just one or two days' worth of storage sitting in the system and the plants are running all the time.”

Globally the water industry is under scrutiny at the moment – more a quality than quantity issue.

“But the two go hand-in-hand. We can't produce massive volumes of high quality water for it to be used in an irresponsible manner.”

Until the restrictions, people were doing exactly what they were entitled to do with water from the city supply lines – that's pretty much anything.

“But since the restrictions, people are being absolutely fantastic and so a big ‘thank you' from me.”

And in the distance, just beyond the horizon, there's the Waiari water supply scheme, another water supply scheme, our third water treatment plant, a $110 million project to irrigate a rapidly growing city.

“That'll help, a big plant, lot of infrastructure, that'll definitely take the pressure off, there'll be a lot more treated water capacity.”

But not for three years, in 2021.

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Reality versus spin, a staff 'dump' on residents.

Posted on 09-01-2018 11:31 | By Murray.Guy

This article is nothing but an attempt to divert attention from the reality of staff incompetence and elected member 'white elephant' prioritisation, JUST as we are experiencing with traffic and stormwater management. To use phrases like 'dumping water on our lawns' (versus controlled sprinkling as we do) gets up my nose somewhat as I very much value a healthy and green environment, the great outdoors being a strength of our region and very much appreciated by many locals and visitors. Rodney suggests we spend $thousands on a water bore and pumps - perhaps Rodney might also ensure this and other collection and water re-use options are encouraged by our Councils rather than apply more obscene fees and consenting processes? Rodney, we have water meters and user pays. Do your job, elected members, put critical infrastructure FOR ALL, before your extravagant nice-to-haves FOR a FEW.

By tabatha

Posted on 08-01-2018 23:54 | By The Caveman

YOU are right on the button - at least 20 odd years with MASSIVE population increase and NOTHING has been done to increase the water supply for the city. What has happened to the WATER RATES paid by all the NEW residential properties over the past 20 years.?? Water rates are WATER rates - ALL water rates should have be spent on providing ADDITIONAL water supplies for the every increasing population - clearly this has not been done and WATER rates have been spent elsewhere !!!

Milimetres of rain ?

Posted on 08-01-2018 18:32 | By Ratepayer

A very useful snippet for gardeners is: 1mm of rain provides 1litre of water per square metre.

Get a water tank at home

Posted on 08-01-2018 14:56 | By MISS ADVENTURE

For the garden, lawns and washing the car. All problems then solved.

Not Planning

Posted on 08-01-2018 11:09 | By tabatha

For 17 years no water problems and the first real hot summer and problems arise. What additional real planning was done during the 17 years. During the that time money should have been put aside to plan for more storage as we all know Tauranga did not stop growing. Does anyone know how many new storage or pumps installed during that time for the increased growth. Once again it seems as though money was spent in wrong areas by other groups of council.


Posted on 08-01-2018 07:29 | By whatsinaname

Why don't the council be honest and say the storage tanks are not big enuff for the growing population. Won't matter how much rain we have. Also collect rain water and don't rely in the streams . My thoughts

A waste of money

Posted on 07-01-2018 21:00 | By Sg1nz

So Old Trucker wants TCC to spend $150M capex, plus another $10 opex pa, so that a few people in Papamoa can water their grass? Look at the graph, average usage is like 25M l a day. So why spend all of that money, plus the people and money to maintain it when we don't actually need it?You need storage and treatment capacity.

Old trucker..

Posted on 07-01-2018 17:38 | By Calm down

As the article says the problem is not storage it's the fact that the plants can't treat the water fast enough to keep up with demand. And that's going to be a problem until the new plant is finished being built.

me wonders

Posted on 07-01-2018 15:28 | By old trucker

Why they cannot build huge roofs over storage tanks to collect it,this Rodney Clark needs his head read, for gosh sake we should put down a bore or harvest it,(NOW Rodney) look at all the people with huge swimming pools who use from 500 litres to 20,000 litres throw your hook at them DONT PUNISH people, if we have a METER we pay so dont blame us,you always having a go at people and say we are being watched, we pay RATES (SO) instead of spending $30 million on a MUeseum build BIGGER STORAGE,also you are getting a NEW COUNCIL BUILDING at blow out price $40 million, if you got RID OF all the DEAD WOOD in TCC we could use that MONEY for STORAGE as well, my thoughts only on this subject,GOSH these TCC NO hopers who run these things make me sick,Thankyou Sunlive,10-4 out. PHEW.

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